Gonadotropin-releasing hormone improves reproductive performance of dairy cows with slow involution of the reproductive tract.

Eighty multiparous Holstein cows were assigned randomly at calving to receive either 100 microg of GnRH or saline 13 or 14 d postpartum (PP). From 4 to 28 d PP the cows' reproductive organs were palpated weekly per rectum, and cows were subclassified within each group as undergoing slow (delayed) cervical and uterine involution (abnormal) or as normal cows. Last milk obtained after removing the milking machine was assayed for progesterone 3 times a week for 120 d PP. Fourteen of the 80 cows were removed from the experiment because of culling or various veterinary treatments of pathologic conditions that could confound analysis of the GnRH treatment effects. As expected, the treatment of normal cows with GnRH had no significant effects on the first estrus or the first estrous cycle PP, on services per conception, days open, or any other reproductive trait measured. However, in the abnormal group of cows receiving saline, first rebreeding after calving was delayed (81 vs. 67 d), fewer were pregnant by 105 d PP (23 vs. 64%), and number of days open was greater (121 vs. 87 d) compared with those receiving GnRH; all were significant (P<.05). Treated abnormal cows were equivalent to the control normal cows. Thus, GnRH given 13 to 14 d PP to cows characterized as undergoing slow involution of the reproductive system, but with no other clinical problems, seems to assist in promoting rapid normal reproductive function. Subsequent losses due to culling were greatly reduced.

Acrosin activity of canine spermatozoa as an index of cellular damage.

Eight experiments were performed to validate an extraction technique for canine acrosin and to quantitate the acrosin activity of fresh and frozen-thawed spermatozoa. Acrosin activity from fresh spermatozoa differed amongst dogs and was influenced by the interval since previous ejaculation. Freezing and thawing spermatozoa induced a loss of acrosin activity that differed with the extender in which the spermatozoa were frozen. The assay of acrosin activity, in conjunction with motility estimates, provides a more complete evaluation of the efficacy of seminal extenders in attenuating freezing injury than do motility estimates alone.